Segui broke in as a regular starter for the A’s in 1962, achieving modest success with a mediocre team. He led the AL in losses in 1964 with an 8-17 mark. In 1969, he was the primary reliever for Seattle in the Pilots’ only season, saving 12 and winning eight in relief. Returned to the A’s the next season, he was used as a reliever and spot starter and led the AL with a 2.56 ERA in 162 innings. The Cardinals acquired him in 1972, and the following year he saved a career-high 17 games. Segui is the only man to play for both the Seattle Pilots and the Seattle Mariners.